This came up in the discussion groups today, a user has a set of points that he needs to create a surface from but the points also have a depth value. He wants to create an additional surface below the original surface but at the depth below as recorded in the point (the depth is not constant, it changes for each point). For example, point 1 is at elevation 100 and has a depth of .55′, point 2 is at elevation 101 and has a depth of .48. The elevations of the first surface would be 100 at point 1 and 101 at point 2. The elevations of the second surface would be 99.45 at point 1 and 100.52 at point 2.

To do this, we’ll need to import the points twice (I would recommend doing this in two separate drawings and then data referencing the surfaces together), once at the original elevation and once at the adjusted elevation. Importing the original points is not a big deal and you can find all sorts of information on how to do this online so I’ll skip it here.

To do the elevation adjustment, we’ll need to know something about the point file. In the example I’m using here, I have a .txt file that is comma delimited and looks like the following:
1,5000, 5000,100,GND,-.55
2,5001,5001,101,GND,-.48
…

The format of this is very common, PNEZD (Point, Northing, Easting, Elevation, Description) but it has the added value of depth to it. We need to create a new Point File Format to import this data. On the settings tab of the prospector, expand out Points, right click on Point File Formats, and choose New. The format type you want is User Point File.

New Point File Format

After you choose In the new point file format, you’ll need to name the format, set up the columns to match the data that you have, and indicate how the file is delimited (a comma in this example). The PNEZD part is pretty straight forward (if you aren’t sure about it, check out one of the other point file formats that come with Civil 3D) but we need to add a column for the depth. The depth will depend on the how the data was collected. In my example, I have a negative sign indicating that the value is to go down so I’ll use the Z+ value. If the value is listed positive and you want it to go down, you’ll need to choose the Z- value.

Point File Format Settings

Now that we’ve done this, we can import the points. In order for the point elevations to be adjusted, we need to tell Civil 3D to actually adjust the elevations. On the Import Points dialog box, down towards the bottom in the advanced options section, there is an option to do elevation adjustments if possible. Makes sure this is toggled on and your points will come in at the adjusted elevations.

Import Points Settings

The following image shows the results of bringing in the same point file once using the elevation adjustment (on the right) and a second time bringing it in without the elevation adjustment (on the left):

With (right) and Without (left) Elevations Adjustments

Hope this helps out and let me know how you are using this. I would really like to know what you’re doing with it!